Description of Resource Recovery Technologies

Appendix C

Description of ResourceRecovery Technologies

In this appendix, the processes for central-ized resource recovery are described and

the major unit processes of the technologiesare identified. Although many processes re-cover both energy and materials, the tech-nologies for each of these purposes are dis-cussed separately here. A list of additionalreadings on resource recovery is included.

This appendix is primarily descriptive. It isbased on published literature and on conver-sations with industry, Government, and otherexperts. Not all of the processes describedhere are in commercial use. See chapter 5 fora discussion of the status of the technologiesand chapter 3 for a discussion of marketing ofrecovered materials and energy.

Energy Recovery Systems

Mass Incineration ProcessesWATERWALL INCINERATION

In waterwall incineration, raw municipalsolid waste (MSW) is burned directly in largewaterwall furnaces, generally without pre-processing the waste. The primary product issteam, which can be used directly or con-verted to electric power, hot water, or chilledwater. Figure C-1 shows schematically themain features of a waterwall furnace for un-processed MSW.

In some installations shredding to reducewaste size and/or facilitate recovery of mate-rials takes place. For example, at the Saugus,Mass. plant, large bulky items have beenshredded before burning. (The shredder isbeing removed, however.) At Hamilton, On-tario MSW is shredded before burning. Fer-

rous metal can be recovered by magnetic separation from ash after incineration, or beforeincineration if MSW is pre-shredded.

Waterwall combustion systems nave beenused commercially in Western Europe sinceWorld War II. Data from a recent survey oftheir experience indicate that Europeanplants tend to achieve large scale usingseveral small modular furnaces. For exam-ple, the 634 tons per day (tpd)* Sorain Cec-chini facility in Rome, Italy has six, 4.4-ton-per-hour units.(2)

This modular approach contrasts with U.S.practice. The Saugus plant has a design ca-pacity of around 1,500 tpd and uses two Euro-pean Von Roll furnaces with a capacity ofaround 31 tons per hour each.

Even though European societies differ fromours, comparisons should be helpful in con-templating future technological directions forU.S. development. The Environmental Protec-tion Agency (EPA) has an intensive, detailedstudy of European systems underway.

SMALL-SCALE MODULAR INCINERATIONSmall-scale modular incinerators feature

heat recovery as steam or hot water, andusually forego materials recovery. Most applacations to date have been in hospitals,schools, other institutions, and industrywhose wastes are more homogeneous thanMSW. Thus, application of this technology toMSW is a relatively recent development.Three of these systems were reported asoperational in EPAs Fourth Report to the

*A1l ton units in this appendix are short tonsz,ooopounds.

254

Appendix CDescription of Resource Recovery Technologies l 255

Figure C-1 .Typical Waterwall Furnace for Unprocessed Solid Waste

Boiler

1- - - - - - - - - - - -

\

UnloadingIS h e d

RefusePit

Congress: a 50-tpd unit at Blytheville, Ark., a30-tpd unit at Groveton, N.H. and a 20-tpd fa-cility at Siloam Springs, Ark.(3)

These systems are called modular becauseindividual furnaces are small and desiredplant size is achieved by installing severalidentical units or modules.(4) MSW is inciner-ated in two stages. First, raw MSW is burnedin insufficient air to achieve complete com-bustion, producing a combustible gas and abyproduct residue. The gas from primarycombustion is then burned with an auxiliaryfuel [oil or gas) in a secondary combustionchamber with excess air. Hot gases from thesecondary combustion chamber are passedthrough a waste heat recovery boiler or heatexchanger to produce steam, hot water, orhot air. The two-stage combustion process, ascontrasted to traditional single-stage incin-eration, helps to reduce particulate emissionproblems.

Air-PollutionControl

IIIIIIIIIIII

tII

IIL

Stack

Refuse-Derived Fuel SystemsSolid refuse-derived fuel (RDF) is produced

by separating MSW and mechanically remov-ing the organic combustible fraction usingwet or dry processes. The fuel product of dryprocessing can be fluff RDF, densified RDF,or dust or powdered RDF depending on thesubsequent processing used. Most RDF plantsalso recover one or more of the followingmaterials; ferrous, aluminum, glass, or mixednonferrous metals. Figure C-2 schematicallyportrays the main processes for producingthe different RDF fuels.

In dry mechanical processing of the typeused in the St. Louis, Me.; Ames, Iowa; andWashington, D.C. facilities, raw waste typ-ically is first shredded to 8 inches or less insize. This shredded material is next putthrough a device called an air classifierthat separates the light organic material from

256 Materials and Energy From Municipal Waste

Figure C-2.This Simplified Flow Diagram Shows How the Dry Processing Approach (No Water Slurry)Can Be Used to Produce Fluff, Densified, or Dust RDF

metals and other heavy organic and inorganicmaterials. The light material then goesthrough a rotating screen or trommel toremove abrasive fine sand, glass, and grit.The heavy materials from the air classifierand trommel move to a magnetic separatingdevice that recovers ferrous material. Someplants also attempt to recover aluminum,glass, and mixed nonferrous metals, usingprocesses described in a later section.

Based on experiences with the first genera-tion of dry waste separation systems thatemployed shredding and air classification, at-tention has recently been given to a widervariety of processing schemes. One includesa trommel, or screening device, as the firstprocessing step, to remove whole cans andbottles prior to waste shredding. In anothervariant, the shredder is eliminated and airclassification is used as a first step. This isbased, in part, on the concept that shredding,which is the locus of most operating explo-sions (see chapter 5), should be avoided. The

Shredder

EmbrittlingAgent

Ball Mill

FluffRDF

DensifiedRDF

Densifier

DustRDF

best arrangement and design of first-stagedry mechanical separation processes is animportant area of current research on re-source recovery.

As shown in figure C-2, the light organicmaterial from the trommel goes to a second-ary shredder that further reduces the parti-cle size to less than 11/z inches. The resultantmaterial is called fluff RDF. Fluff RDF canbe passed through a pelletizing or briquettingmachine to yield densified RDF. The objec-tive of densification is to improve storage,handling, and stoker-furnace burning charac-teristics. Alternatively, the light output fromthe trommel can be treated with a chemicalembrittling agent and ground to a fine pow-der in a ball mill to produce a dust or pow-dered RDF with a particle size of around0.15 mm. This is the basis of the CombustionEquipment Associates ECOFUEL-HQ process.

Figure C-3 illustrates the wet process RDFmethod. With this technology raw refuse is


Figure C-3. Wet Process Energy Recovery System

Cone

Barrel Press

Tipping Floor

Junk Remover &

vNonferrousMaterials

Small Ferrous MetalsGlass (by Color)

SOURCE (1}RecoveredFerrous Metal

fed to a hydropulper (a machine like an over-sized kitchen blender] where high-speed ro-tating cutters chop the waste in a water sus-pension. Large items are ejected and the re-maining slurry is pumped into a liquid cy-clone separator where smaller heavy mate-rials are removed. Water is then removed toleave wet RDF with from 20- to 50-percentwater content, which can be burned alone oras a supplement to coal, depending on itswater content.

The wet pulping method has several advan-tages and disadvantages relative to the dryprocess. Sewage sludge can be mixed withthe wet pulp prior to dewatering and theresulting mixture can be burned as a methodof codisposal. Dewatering, however, is expen-sive and energy intensive. The wet processreduces the likelihood of explosion or fire inthe size reduction phase, as compared to drymechanical processing. It is possible to re-cover some organic fiber by the wet process.However, the quality of this fiber is insuffi-cient for it to be used to produce paper. The

only domestic application in one small plantat Franklin, Ohio, has been as a reinforce-ment in roofing material.

Pyrolysis SystemsPyrolysis is destructive distillation or de-

composition of organic materials in MSW atelevated temperatures in an oxygen deficientatmosphere. The product of pyrolysis is acomplex mixture of combustible gases, liq-uids, and solid residues usable as fuels orchemical raw materials. The characteristicsof the pyrolysis products depend on such vari-ables as time in the reactor, process tempera-ture and pressure, oxygen content of the gasin the reactor, particle size of the MSW feed,and the choices of catalysts and auxiliaryfuels. Differences in these parameters dis-tinguish the several proprietary processesthat have been developed, Four proprietarysystems are presently in some stage of dem-onstration. Two of these produce low-Btu gas:Monsantos Landgard and the Andco Torrax

258 l Materials and Energy From Municipal Waste

processes. The Union Carbide Purox systemproduces medium-Btu* gas. The OccidentalResearch Flash Pyrolysis process produces aliquid fuel.**

In the Monsanto system, figure C-4, MSWis shredded before it is pyrolized with a sup-plementary fuel in a large (20 ft diameter, 100ft long) horizontal, refractory-lined kiln. Solidresidue from the kiln is water quenched andseparated into ferrous metal, glassy aggre-gate, and char. The char is dewatered andlandfilled. In the Andco process, figure C-5,

*Low.Btu gas has a heating value of around 100 to150 Btu per standard cubic foot (scf), the heating valueof medium Btu gas is 300 to 400 Btu per scf. By com-parison, natural gas has a heating value of about 1,000Btu per scf.

**Liquid pyrolysis oil has a heating value of about10,000 Btu per pound, roughly half that of No. 6 fuel oil.

raw MSW enters a vertical shaft furnaceafter large items are removed and is pyro-lyzed with auxiliary fuel. As the charge de-scends it is dried and converted to gases,char, and ash. The low-Btu gas producedmust be burned onsite to produce steam orhot water.

The only Monsanto system in operation, al,000-tpd plant in the city of Baltimore, is cur-rently undergoing modification to solve airpollution and other technical problems. Mon-santo has withdrawn from the project. Andcohas no plants in the United States. A 200-tpdplant is in startup in Luxembourg, and twoothers are under construction, one in Franceand one in West Germany.

In the Union Carbide Purox system, figureC-6, ferrous material is magnetically sepa-

Figure C-4.The Monsanto Landgard System Produces a Low-Btu Gas Which is ImmediatelyBurned Onsite for the Production of Steam

Afterburner

Air-ollution ControlWaste Heat n

Boiler A H Stack

rGlassy Aggregateand Char

ruul U I I

L) 1 =Magneticsfor Sale

Shredding


Air

Figure C*5. Torrax Slagging Pyrolysis System

SolidWas te

a

Electrostatic

I I

Compressor Slag- Tap Secondary Combustion ChamberInert Residue

ratecl from shredded MSW prior to feeding.Shredded refuse fed into the top of the ver-tical shaft furnace descends by gravity intozones of increasing temperature where dry-ing. then pyrolysis, and finally char combus-tion and slagging take place. The temperaturein the bottom zone, the slagging zone, is highenough to reduce the residual to a molten slagthat continuously drains into a water quenchto produce a hard granular aggregate mate-rial called frit, The Purox process feeds thefurnace pure oxygen, rather than air as in theMonsanto and Torrax systems, and producesmedium-Btu gas product. Its smaller volumeand higher Btu content facilitates economicshipment over reasonably long distances.Union Carbide has been operating a 200-tpddemonstration plant at Charleston, W. Va.,but no commercial facility yet exists.

In the Occidental liquid fuel pyrolysis proc-ess, shown in figure C-7, raw MSW is first

shredded and air classified to recover fer-rous metal, aluminum, and glass prior to py-rolysis. The light organic fraction is dried,shredded again in an inert gas atmosphere,and then introduced to the pyrolysis reactor.Pyrolysis in the reactor vessel produces anoil-like fluid somewhat comparable to No. 6fuel oil* that can be burned in existing oil-fired, steam-electric powerplants. A 200-tpddemonstration plant in San Diego County,Calif., was reported to be undergoing opera-tional testing in early 1978. A subsequentreport in May 1978 indicated that this systemwas not operating and faced major cost in-creases if it were to be continued.(5)

Biological SystemsThis description focuses on three biological

waste-to-energy technologies: recovery of*Ibid,

260 . Materials and Energy From Municipal Waste

Shredder

w~ - I 1 II

)l * * * 9 * * * l * * * * *ll

Product Gasto User

:er

methane from landfills, anaerobic digestion,and hydrolysis.

METHANE PRODUCTION FROM LANDFILLS

Natural decomposition of MSW in landfillsproduces a gas composed of roughly 50-per-cent methane and 50-percent carbon dioxide.If landfill geological characteristics are sat-isfactory, gas can be withdrawn throughwells drilled into the landfill and can betreated to remove moisture, hydrogen sulfide,and other contaminants. Carbon dioxide canbe removed leaving pipeline quality methane.Corrosion problems with this technology ap-pear to be under control.(s) Recovery of meth-ane from an old sanitary landfill is being ex-plored at the Pales Verdes landfill at Los

Angeles where approximately 500,000 cubicfeet of purified methane is being recoveredper day. Enough methane is recovered dailyat the Pales Verdes site to meet the energyneeds of some 2,500 homes.(5) EPA is evaluat-ing several landfill gas-producing projects.(3)

ANAEROBIC DIGESTIONMethane can be recovered from anaerobic

digestion of MSW in large tanks or reactorsas shown in figure C-8. Anaerobic digestion ofwaste is accomplished by two types of bac-teria: (i) acid formers that convert waste toorganic acids, and (ii) methane producersthat convert the acids to carbon dioxide,methane, and small quantities of other gases.One of the potential problems with methane


Figure C7.Production of Liquid Fuel From Solid Waste Using the Occidental Process

PrimaryCla

AirIssifier

WasteLights

Dryer

Trommel II

To Aluminum GlassRecovery

To Steel CompanyFroth

Flotation

Residuals

To Landfill

SecondaryShredder

Pyrolysis

L

Reactorz

6

1

Product

Liquid Fuel

SOURCE (1) To Glass Company

generation is that MSW sometimes containstoxic components that can kill the methane-producing bacteria, Successful methane pro-duction from sewage sludge and animal ma-nure can in part be attributed to the homo-geneity of these substances and to the ab-sence of bacteria-killing toxic contaminants.

A demonstration project to assess the fea-sibility of a 100-tpd anaerobic digestion sys-tem for MSW is being supported by the De-partment of Energy (DOE) at Pompano Beach,Fla., with startup expected in late-1978. Atthe Pompano Beach facility, MSW will be pre-processed to produce fluff RDF and recoverferrous metal, The wet RDF process couldalso be used. The RDF will be mixed with raw

sewage sludge and introduced into digestertanks where it is mixed. The MSW-sludge mixwill stay in the reactor around 10 days to cap-ture the largest port ion of the methane;longer retention times will produce more gasbut at a rapidly decreasing rate. The gas pro-duced by this process will contain approx-imately 50-percent methane and 50-percentcarbon dioxide with a heating value of 540 to700 Btu per cubic foot. The gas can be burnedas is, without purification, or with furtherprocessing the carbon dioxide and traces ofhydrogen sulfide can be removed to yieldmethane with a heating value of about 1,000Btu per cubic foot. The digestion process pro-duces large quantities of a liquid effluent, themajority of which will be recycled to the mix-

262 l Materials and Energy From Municipal Waste

Figure C-8.Biological Gasification of Solid Waste in Reactors

Light Fraction

Fracfion

Ferrous ScrapMarket

Sanitary Landfill

ing tanks, with the remainder discharged to acity sanitary sewer system, The remainingsolids, about 17 percent of the refuse feed,must be either landfilled or burned in special-1y designed boilers. Schulz (6) estimates thatapproximately 3,700 cubic feet of methanewill be produced per ton of MSW.

HYDROLYSIS

There are two processes for the productionof ethyl alcohol (ethanol) from the organicportion of MSW by hydrolysis: (i) acid hydrol-ysis, which is a welI-developed industrialtechnology for nonwaste applications, and (ii)enzyme hydrolysis, a recent process still inthe research stage. To convert cellulosic ma-

Sewage Residue toBiender S i u d g e Dewateringand Landfiii

Gas Output

rs

terial to ethanol, it must first be hydrolyzed toproduce sugar which then ferments to yielddilute ethanol that can be recovered by dis-tillation. The production of ethanol fromMSW by hydrolysis is not currently in thecommercial or demonstration stage to ourknowledge. Wilson (7) reports that BlackClawson is currently researching this area.

Considerable pioneering research in en-zyme hydrolysis has been carried out at theU.S. Army Natick Development Center inMassachusetts. Naticks work in this areaarose out of attempts to prevent biologicaldecay of textile materials. Since 1972, theyhave been authorized to conduct studies ofenzyme hydrolysis processes for converting


cellulose wastes of military bases into usefulproducts. The fungus Trichoderrna viride hasbeen identified as having considerable en-zyme productivity, with a potential for com-mercially feasible conversion processes.(8)

In addition, the Gulf Chemical Company ispresently exploring the feasibility of con-structing a demonstration plant (50 tpd of bio-mass feedstock) for the production of ethanolfrom municipal, agricultural, and industrialwaste by enzymatic hydrolysis.(g)

Materials Recovery Systems

s everal of the energy recovery systems justdescribed include ferrous metal, alumi-num, or glass recovery technologies. Othermaterials that can be recovered are paperfiber, compost, and other nonferrous metals.

AluminumThe process for aluminum recovery is

based on an eddy current separation systemcommonly called an aluminum magnet. Withthis technology, nonferrous conducting met-als mixed with other wastes are conveyedthrough a magnetic field in such a way thatan eddy current is induced in the metals. Thiscurrent causes the metallic conductors to berepelled from the region of the magnetic fieldand thus out of the conveyor path. Nonmetal-lic are unaffected and are carried on. Thedevice is quite sensitive and can be tuned torepel various shapes, densities, or materials.For example, it can be tuned, or optimized, torecover aluminum cans, the largest part ofthe aluminum waste. Eddy current separationequipment is currently installed at the follow-ing locations: National Center for ResourceRecovery (NCRR) experimental test facility inWashington, D. C.; Ames, Iowa; BaltimoreCounty, Md.; Occidental pyrolysis plant inSan Diego, Calif.; the Americology plant inMilwaukee, Wis.; and in New Orleans, La. Asreported in chapter 5, as of April 1978, noneof these facilities was in steady productionwith a sustained commercial run.

Electrostatic separation is another methodfor separating nonferrous metals from or-ganic materials. Mixed wastes pass betweencharged plates and are given an electriccharge. Conducting materials such as alumi-num lose their charge on an electricallygrounded drum and fall off. Nonconductorsretain their electrical charge and adhere tothe drum. None of these systems is in use infull-scale plants. To further assist in cleaningcontaminants from metals, a device called anair knife is sometimes used.

GlassTwo systems are being experimented with

for the recovery of waste glass from MSW.Research is preceding on froth flotation, astandard mineral processing technique, forthe recovery of glass. In this process theheavy portion of the waste stream, rich infinely ground glass, is slurried in water alongwith chemicals that cause the glass to be-come attached to air bubbles on the surfaceof the water. The glass floats out of the mixwith the bubbles and is then washed anddried. Froth flotation is being explored at theNCRR facility in Washington, D. C.; in NewOrleans, La.; and at the Occidental pyrolysisplant in San Diego. It is being installed in boththe Monroe County, N. Y., and the Bridgeport,Corm., plants.

Since glass recovered by froth flotationproduces mixed colored cullet, which has alimited market, the process of optical sort-ing is being examined. Glass particlesaround one-fourth inch in size are sorted, onthe basis of their light transmission proper-ties, into three colors, clear (flint), green, andamber. This process currently faces prob-lems with high costs and its inability to rejecta sufficiently large fraction of contained ce-ramics and stones to meet the quality stand-ards required by glass producers. It also can-not recover particles smaller than one-fourthinch in size. Color sorting is being installed atthe Hempstead plant in New York and hasbeen used on a pilot plant basis at the Frank-lin, Ohio, facility.

264 . Materials and Energy From Municipal Waste

Ferrous MetalsFerrous metals have been removed from

MSW by magnetic separators for a number ofyears. A recent study by the American Ironand Steel Institute identified nearly 40 suchcommercial installations in the UnitedStates. (I()) Some experience has been gainedmore recently in magnetic recovery of incin-erated ferrous metals from the residue or ashfrom MSW incinerators. Such a device is cur-rently in regular operation at the Saugus in-cinerator, but the recovered ferrous materialis not currently being marketed. The U.S.Bureau of Mines has experimented with acomplex mineral-technology-based processfor back-end recovery of a variety of mate-rials from incinerator residue.(11) Inciner-ated ferrous may be less marketable than theunincinerated product.

CompostComporting permits organic matter to de-

cay to humus, which can be used for fertilizeror soil conditioner. Generally, comporting hasnot been economically successful because ofdifficulty in selling the humus product. Ac-cording to EPA, only one comporting plantwas operating as a commercial facility in1976, the 50-tpd plant at Altoona, Pa.(3) A1969 survey identified 18 plants with a totalcapacity of 2,250 tpd, indicating a majordecline in U.S. comporting operations in this7-year period.(12)

Comporting is successful in some Europeancountries. In the Netherlands where marketsfor humus in the flower and bulb industriesare good, the Government runs comportingoperations. A technique for briquetting andjoint comporting of MSW and sewage sludgehas been developed in Germany. Its devel-opers claim that the dried briquets can beused in food for pigs, as a soil conditioner, asa stable element in landfills, or as fuel.(2)

FiberNot many centralized resource recovery

facilities can reclaim fiber from MSW forrecycling as fiber. A 150-tpd demonstrationfiber recovery facility has been operatingsince 1971 at Franklin, Ohio, using the BlackClawson wet process described earlier. Fiberrecovered with this process is of poor quality,and it is sold to a nearby manufacturer ofasphalt-impregnated roofing shingles. Twowet process plants, the Hempstead, .N.Y., fa-cility now under construction, and the plantin Dade County, Fla., about to begin construc-tion, will recover the fiber for use as a fuel,not for paper production.

A dry process for recovering paper fiberand light plastics has been developed by theCecchini Company in Rome, Italy. Paper fromthis process is used with straw to make a low-grade paperboard. In general, the quality ofthe recovered paper is low and it has limitedmarketability. Roughly 23 percent of thepaper in the input waste stream is recov-ered.(l) Other dry paper recovery processes,such as the Flakt process, which are being ex-plored on a pilot plant basis in WesternEurope, are described by Alter.(13)

Finally, some of the most recent plants(Milwaukee and New Orleans) feature limitedpaper recovery by hand-packing of bundledpaper from the resource recovery plant inputconveyor. This method has both economic andquality limitations.

Other Materials Recovery TechnologiesThere are many other materials recovery

technologies which have not been addressedin this brief overview. The most importantcontemporary processes, however, have beentouched upon. Readers wishing to explorefurther might do well to start with a review ofthe extensive research in this area carriedout over the years by the U.S. Bureau ofMines.(11)


Additional Reading on Resource Recovery Technologies

1. Alter, H., and E. Horowitz, (editors) Re-source Recovery and Utilization, (ASTMSpecial Technical Publication 592, pro-ceedings of the National Materials Con-servation Symposium, 29 April - 1 May19740

2. Environmental Protection Agency, TheResource Recovery Industry: A Survey ofthe Industry and its Capacity, report SW-50/c, 1976.

3. Engineering and Economic Anal-ysis ofWaste to Energy Systems, a reportby the Ralph M. Parsons Company, June1977.

4. , St. Louis Demonstration FinalReport: Refuse Processing PlantAssess-ment of Bacteria and Virus Emissions byMidwest Research Institute, Kansas City,Me., draft report August 1977. EPA Con-tract No. 68-02-1871, MRI Project No.4033-L.

5. , St. Louis Demonstration Final Re-port: Refuse Processing Plant Equipment,Facilities, and Environmental Evaluations,by Midwest Research Institute, Kansascity, Mo,, September 1977. EPA-600 /2-77-155a.

6. Evaluation of the Ames SolidWaste Recovery System, Part 1. Summaryof Environmental Emissions: Equipment,Facilities, and Economic Evaluations, byIowa State University and Midwest Re-s e a r c h I n s t i t u t e , N o v e m b e r 1 9 7 7 .EPA-600/2-77-205.

7 Levy, S. J., and H. G. Rigo, Resource Re-covery Plant Implementation Guides forMunicipal Officials, Technologies Report,U.S. EPA, SW-157.2, 1977.

8. Mantell, C. L., Solid Wastes: Origin, Col-lection, Processing, and Disposal, JohnWiley, 1975.

9. Schulz, H., J. Benzier, B. Borte, M. Neo-matalla, R. Szostax, and R. Westerhoff,Resource Recovery Technology for UrbanDecision Makers, prepared for the Na-tional Science Foundation by the UrbanTechnology Center, School of Engineeringand Applied Science, Columbia Universi-ty, H. W. Schulz, et al., January 1976.

10. Pavoni, J,, J. Heer, and D, Hagerty, Hand-book of Solid Waste Disposal, VanNostrand, 1977.

11. Resource Recovery From Municipal SolidWaste, A State of the Art Study, NationalCenter for Resource Recovery, Inc., Lex-ington Books, 1974.

12. U.S. Department of the Interior, Bureau ofMines Research on Resource RecoveryReclamation, Utilization, Disposal andStabilization, Bureau of Mines Informa-tion Circular (IC 8750), 1977.

13. Weinstein, N. S., and R, F. Toro, ThermalProcessing of Municipal Solid Waste forResource and Energy Recovery, Ann Ar-bor Science Publishers, Inc., 1976.

266 l Materia/s and Energy From Municipal Waste

References

1. Environmental Protection Agency, Re-source Recovery Plant Implementation:Guides for Municipal O~~icials, Technol-ogies Report, No. SW-157.2. Second print-ing 1977.

2. Department of Energy, European Waste-to-Energy Systems, An Overview. ReportNo. CONS-2103-6 prepared by ResourcePlanning Associates, Inc., June 1977.

3. Environmental Protection Agency, Officeof Solid Waste Management, Fourth Re-port to the Congress, Resource Recoveryand Waste Reduct ion , PublicationSW-600, Aug. 1, 1977.

4. Hofmann, Ross, Associates, Evaluation ofSmall Modular Incinerators in MunicipalPlants, Report SW-l13c, done for EPA byRoss Hofmann Associates, Coral Gables,Fla., 1976.

5. Schwegler, Ron, Division Engineer,County Sanitation District of Los AngelesCounty, Calif., telephone communication,May 1978.

6. Schulz, H., J. Benziger, B. Bortz, M. Neo-matalla, R. Szostak, G. Tong, G., and R.Westerhoff, Resource Recovery Technol-ogy for Urban Decision Makers, a reportproduced by the Urban Technology Cen-ter, Columbia University, for NSF, Janu-ary 1976.

7. Wilson, E. M., J. Leavens, N. Snyder, J.

Brehany, and R. Whitman, Engineeringand Economic Analysis of Waste toEnergy Systems, a report prepared byRalph M. Parsons Co. for the EPA In-dustrial Environmental Research Labora-tory, Cincinnati, Ohio, June 1977. (Avail-able as EPA- 600/7-78-086, May 1978.)

8. Gaden, E. L., M. H. Mandels, E. T. Reese,L. A. Spano, (editors) Enzymatic Conver-sion of CeM.dosic Materials: Technologyand Applications, Symposium Proceed-ings held at Newton and Natick, Mass.,Sept. 8-10, 1975. John Wiley and Sons,

. 1976 .9. Solid Waste Report, July 31, 1978, p. 125.

10. American Iron and Steel Institute,Summary Report of Solid Waste Process-ing Facilities AISI, Washington, D. C.,1977.

11. U.S. Bureau of Mines, Bureau of MinesResearch on Resource Recovery Reclama-tion, Utilization, Disposal, and Stabiliza-tion, U.S. Dept. of the Interior, Bureau ofMines Information Circular 8750, 1977.

12. Pavoni, J., J. Heer, and D. Hagerty, Hand-book of Solid Waste Disposal, Van Nos-trand, 1977.

13. Alter, H., European Materials RecoverySystems, Environmental Science andTechnology, vol. 11, no. 5, May 1977.

Documents

Description of Resource Recovery Technologies